Preliminary Results on the Plantar Flexion during Grand-Plié in Ballet Dancing with Inertial Measurement Units

The incorrect execution of technical movements in ballet dancing leads to artistical errors and potential injuries. Among the existing exercises performed during training, the plié is the most common, as it is taught even to the youngest students. In this work, we analyze the plantar flexion of three female volunteers with different levels of preparation (professional, academy, amateur) during repeated executions of a grand-plié in fifth position, first while holding the barre with the left hand and then with the right one. The system employed for the measurements is the MVN Link hardware model by Xsens Technologies, which is a suit equipped with seventeen magneto-inertial measurement units (MIMU). The maximum plantar flexion reached during the grand-plié is 24.8±2.7° for the professional dancer, 42.9±2.2° for the academy student, and 47.2±9.2° for the amateur dancer. The amateur dancer only exhibits an evident asymmetric behaviour (56.1±6.9° for the left plantar flexion and 39.9±2.4° for the right plantar flexion with the left hand at the barre, 54.5±2.9 for the left plantar flexion and 38.1±1.7° for the right plantar flexion with the right hand at the barre). The results show that it is possible to identify incorrect executions, such as the ones caused by excessive or asymmetric plantar flexion, that can lead to injuries.